Big fish

No, I wasn't dreaming. As walked by the Ravensbourne next to Cornmill Gardens I noticed fish somewhat bigger than usual in the water. Then I noticed there were a lot more fish than I'm used to seeing in this river.

I'm pretty sure they were trout, and as they were all struggling upstream, I wonder if they are spawning?

In any case, an impressive sight. Does anyone know if they were trout? If so, is this a recent occurence? Is the river cleaner of late?